1. Field of the Invention
The present invention relates generally to telecommunications data time division multiplexed backplane systems. More particularly, the present invention relates to backplane multiplexing systems and methods capable of internetworking bit serial, byte parallel, and packet based products.
2. State of the Art
Apparatus for time division multiplexing (TDM), and their use in the backplanes of telecommunications systems have been known in the arts for some time. Typically, in backplane systems, time division multiplexers are comprised of interfaces to a plurality of channels, buffers for incoming and outgoing information, and a frame processor which includes a memory means and a recirculating counter which addresses the memory means. The frame processor is used to select information from the plurality of channels for sending over the backplane toothers of the channels according to a desired framing algorithm. Many different framing algorithms are known in the art, such as are disclosed in commonly owned U.S. Pat. No. 4,888,770 to Bains, U.S. Pat. No. 4,885,745 to Gordon, and U.S. Pat. No. 4,727,536 to Reeves et al. which are hereby incorporated by reference herein in their entireties. As is known in the art, the constant bit rate information which is multiplexed over the backplane in this manner may be bit serial, or nibble or byte parallel.
More recently, it has become desirable to provide multiplexers for packet-based LAN (e.g., ETHERNET) and ATM data (these multiplexers being called "routers" because the LAN and ATM packets have the destination addresses imbedded in the packets). While ATM data is of a fixed packet size, LAN data can assume any of various formats which provide different sized packets. In order to accommodate LAN and other bursty packet-based telecommunications traffic, equipment utilizing packet-based backplane buses have been provided. However, these packet-based backplane busses have existed completely apart from the TDM backplane busses, and are rarely, if ever, found in a single piece of equipment; and there are certainly no known backplane systems which accommodate both TDM bit and/or byte data, and packet-based data on a single backplane bus. Thus, various efficiencies which can be obtained by the merging of the TDM and packet-based "worlds" such as the sharing of common bus drivers and receivers and backplane bus resources have been unrecognizable.